The invention relates generally to marine engines, and more particularly, to propeller hubs.
Outboard engines include a drive shaft which extends from the engine power head, through an exhaust case, and into an engine lower unit. The lower unit includes a gear case, and a propeller shaft extends through the gear case. Forward and reverse gears couple the propeller shaft to the drive shaft. The drive shaft, gears, and propeller shaft sometimes are referred to as a drive train.
A propeller is secured to and rotates with the propeller shaft. Torque from the propeller is transmitted to the shaft. Specifically, propeller hub assemblies transmit torque to the propeller shaft. Exemplary propeller hub assemblies include cross bolts, keys, shear pins, plastic hubs, and compressed rubber hubs. Such hub assemblies should have sufficient strength or stiffness so that during normal engine operations, very few losses occur between the propeller shaft and the propeller. Such hub assemblies, however, also should be resilient so that the engine drive train is protected in the event of an impact, e.g., if the propeller hits a log or rock.